1. Field of the Invention
The invention relates to techniques for purifying combustion-exhaust gas emitted from a fuel reforming device, which supplies a fuel cell with reformed fuel.
2. Description of Related Art
One known method that reforms an original or pre-reformed fuel and generates reformed fuel (hydrogen-rich gas) uses steam produced within a fuel reforming device. To produce the steam in this water-vapor reforming method, the fuel reforming device includes a heater for burning exhaust gas emitted from a fuel cell, so-called “anode-off and cathode-off gases”, or for burning a portion of the pre-reformed fuel to be reformed by the fuel reforming device. Exhaust gas emitted from the fuel reforming device as a result of combustion of the anode-off and cathode-off gases or the pre-reformed fuel, more precisely, an exhaust gas emitted from the heater of the fuel reforming device is discharged into the atmosphere, without any treatment to purify the exhaust gas.
However, the above-described fuel reforming device suffers from a problem that the exhaust gas emitted from the fuel reforming device contains an unburned fuel component and carbon monoxide, though the contents of the unburned fuel component and carbon monoxide are smaller than those contained in an exhaust gas emitted from an internal combustion engine. In view of an expected increase of demand for fuel cells and a consequent increase of the total volume of the exhaust gases emitted from the fuel reforming devices for the fuel cells, there is a need for a suitable treatment for purifying the exhaust gas emitted from the fuel reforming device, from the standpoint of air pollution control (atmospheric contamination control) and ecology.